From the practice, stepped transmission are known which are operated either partially automated or fully automated wherein one automatic cycle of a gear change by the stepped transmission particularly results in relief of the driver. Especially in fully automated selector transmissions or stepped automatic transmissions, control operations like “uncoupling/starting” and “gear change” are carried out automatically according to established or adaptive programs. For reasons of comfort, it has been changed to carrying out gear changes without noticeable interruption of traction.
Such stepped automatic transmissions, where the transition from one ratio step to another is executed without interruption of the power flow in a drive line, are also designated as force-locking transmissions or powershift transmissions. Additional brake and clutch components of the powershift transmissions make a coupling of the ratio steps under load possible. In a powershift, the step to be discontinued is uncoupled from the positive engagement while the new step is coupled parallel therewith in the power flow of the stepped automatic transmission. A drop in traveling speed advantageously does not occur materially during power shifts since the gear to be engaged is connected with the transmission shaft positively and without drop of the drive torque.
The added brake and clutch components are designed as frictionally engaged shifting elements, such as belt brakes, multi-disc brakes or multi-disc clutches since, with said elements, it is possible to carry out so-called overlapping gear shifts because of the variable transmitting capacity.
The shifting components of the powershift transmission, designed as multi-disc brakes or multi-disc clutches, are controlled via a hydraulic control system with a pressure medium source. The pressure medium source or hydraulic pump of the stepped automatic transmission is also provided for oil supply of a stepped automatic transmission; the hydraulic energy produced by the hydraulic pump is used for closing and retaining the multi-disc brakes or multi-disc clutches, the same as for supplying the stepped automatic transmission with lubricant. A power intake of the hydraulic pump is essentially determined by the oil amount delivered and the hydraulic pressure needed for control of the powershift transmission.
It is disadvantageous that the hydraulic pump of a stepped automatic transmission constitutes an essential source of loss, the energy losses on the side of the hydraulic pump being particularly very high when power shift elements of a stepped automatic transmission are loaded with its closing pressure or retaining pressure so as to keep them in closed state with a high transmitting capacity.
The task of the instant invention is to make a method and a device available for controlling a shift component of a stepped automatic transmission with which gear shifts can be carried out free of interrupted traction and with which energy losses of a stepped automatic transmission can be reduced.